This is a new application for a Pediatric AIDS Clinical Trials Unit (PACTU) that will involve collaboration between the University of Alabama at Birmingham, Emory University in Atlanta and the Medical College of Georgia in Augusta. Investigators with active programs of research and clinical care for infants, children, adolescents and pregnant women with HIV infection will collaborate to form the Southeast PACTU. The Southeast PACTU will bring established programs of research on perinatal infections, antivirals and HIV pathogenesis to the PACTG. The Southeast PACTU will focus on linkage of state-of-the-art laboratory approaches for study of pathogenesis to clinical trials aimed at prevention of perinatal transmission and interruption of primary infection. The Southeast PACTU can contribute the following to the PACTG: (1) Experience translating advances in basic research into tools that can be used to investigate pathogenesis of HIV infection. (2) A record of international leadership in antiviral clinical trials, including phase I antiviral trials in newborns. (3) A distinguished record of achievement in clinical and laboratory studies of congenital and perinatal viral infection. (4) Prior experience with PACTG clinical trials. (5) Leadership in a national collaborative study of HIV natural history in adolescents. (6) Basic and clinical research in major opportunistic pathogens (CMV, HSV, varicella, S. pneumoniae, T. gondii). (7) A new source of clinical trial participants from a region that is under-represented in the PACTG, through established programs that currently reach the majority of women and children with HIV infection in Alabama and Georgia.